In conventional wireless communications systems, mobile devices or other user equipment transmit information to a network, and receive information from a network, such as via a base station. In some networks, the base stations, or other network entities which transmit information to the user equipment, may include different antenna configurations, such as different numbers of antennas, e.g., one antenna, two antennas or four antennas, and/or may transmit the information in accordance with different transmission diversity schemes. In this regard, a base station with a single antenna may transmit information without any transmission diversity scheme, while base stations with two or four antennas may transmit information in accordance with a transmission diversity scheme or a specific transmission diversity scheme out of a set of different available transmission diversity schemes. In order to effectively receive information from a base station, for example, the user equipment must know or recognize the antenna configuration and/or the transmission diversity scheme utilized by the base station. A mobile device may be able to effectively demodulate a received signal only after correctly determining the antenna configuration, i.e., the number of transmit antennas and/or the transmission diversity scheme of a base station. Since the antenna configuration information is needed in order to effectively demodulate the received signal, the antenna configuration information must be determined by the user equipment with very high reliability.
For example, in an Evolved Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access Network (E-UTRAN), the user equipment can gather antenna configuration information regarding the base station, termed an eNodeB in E-UTRAN, using data contained within orthogonal frequency division multiplexing (OFDM) symbols of a message. By way of example, the technical specifications of the Third Generation Partnership Project (3GPP) and, in particular, 3GPP TS 36.211, REL 8 and 3GPP TS 36.212, REL 8 allows for an approach for providing antenna configuration information. In this regard, the user equipment can extract antenna configuration information from provided reference signals or by attempts to decode data within a physical broadcast channel (PBCH).
In E-UTRAN, the eNodeB does not explicitly inform the user equipment of the number of antennas and, in turn, the transmission diversity scheme. Instead, the user equipment can generally analyze the provided reference signals in an effort to determine the number of antennas and/or the transmission diversity scheme employed by the eNodeB. In general, reference signals are placed throughout a sub-frame, within the PBCH and otherwise, according to the number of transmit antennas at the base station. The reference signals are mainly intended to be used for channel estimation purposes. Regardless of a reference signal's location within the sub-frame, detecting the presence of a reference signal can allow, in some instances, user equipment to determine the number of transmit antennas at the base station. However, such a procedure may not always be reliable at the low signal-to-noise ratio conditions where the PBCH is designed to operate.
While, in some instances, antenna configuration information can be derived from reference signals, the user equipment is, at least initially, not aware of the antenna configuration and/or the transmission diversity scheme prior to receiving and demodulating the PBCH. Further, since the antenna configuration information is needed to properly demodulate data and control channels, data loss and latency can result if the user equipment incorrectly identifies the antenna configuration and/or the transmission diversity scheme or if the user equipment is slow in identifying the antenna configuration and/or the transmission diversity scheme. As a result, some user equipment is designed to make assumptions regarding the antenna configuration and/or transmission diversity scheme. These assumptions of antenna configuration and/or transmission diversity scheme may be made prior to, or during demodulation of the PBCH and may not always be correct. In this regard, user equipment may reach an assumption regarding the antenna configuration and/or transmission diversity scheme based on a subset of the information in the PBCH. For example, in some instances, an early PBCH decoding scheme may be utilized which uses information gathered from the first of four bursts of information comprising the PBCH.
However, even when an incorrect assumption is made regarding the antenna configuration and/or the transmission diversity scheme, the error is not always readily apparent upon demodulation and decoding. In some instances, the PBCH can be properly demodulated and decoded even when an incorrect assumption has been made. This situation is referred to as a false detection. In these situations, the user equipment has no means for detecting the erroneous assumption. As such, the user equipment can continue to use an incorrect assumption in further communications resulting in poor performance.
In addition to the issues that come as a result of the user equipment blindly selecting an antenna configuration and/or a transmission diversity scheme, noise in the signal associated with the PBCH can also generate errors. In low signal-to-noise ratio conditions the combination of an incorrect assumption and data corrupted by noise can result in a demodulated and decoded PBCH that appears to be correct. Further, in the same conditions, an accurate assumption with respect to antenna configuration and/or transmission diversity can appear to be incorrect due to the presence of noise. However, some of these cases may be identified by the user equipment because the PBCH is protected by cyclic redundancy check (CRC) bits. It is common for the CRC associated with the PBCH to contain 16 bits. In this regard, some of the errors resulting from a low signal-to-noise ratio can be identified when the CRC check is performed. However, noise can also affect the CRC bits which can further result in erroneous conclusions as to the correct antenna configuration and/or transmission diversity scheme.
Thus, in order to avoid or reduce the loss of data and communication latency, it would be desirable to provide an improved technique for more reliably determining the antenna configuration and/or transmission diversity scheme of a network entity, such as a base station. In particular, it would be desirable to provide a mechanism for determining the antenna configuration and/or the diversity scheme of base station, such as an E-UTRAN eNodeB, that results in a substantially high reliability for determining if the correct assumption regarding antenna configuration and/or transmission diversity has been made.